Although the present invention can be applied to a wide variety of turf maintenance equipment, one particularly advantageous application is power turf mowers. Many types of power turf mowers are known. Such equipment can generally be classified according to the type of cutting unit(s). Typically, the cutting units of a turf mowing machine are either of the rotary, reel or flail type. Reel units are normally used for high precision cutting situations whereas flail units are normally used in severe situations such as roadside mowing. Rotary units, on the other hand, are useful over a wide variety of conditions. Therefore, although the present invention could be used in conjunction with turf maintenance machines and harvesters of any type, for the sake of brevity the invention will be described in terms of a turf mowing machine having one or more rotary cutting units or decks.
Power turf mowing equipment can also be categorized based on the method of propelling the cutting unit. Generally, there are walk-behind; riding; and towed cutting unit mowers. The present invention relates to the latter two types, and particularly to riding mowers; walk-behind mowers are usually found in residential settings, and the present invention does not pertain to such mowers. Thus, for the sake of brevity the invention will be described in terms of riding rotary mowers.
Larger rotary riding mowers typically include a traction vehicle supported by a plurality of wheels; a prime mover connected through a transmission to one or more of the wheels; one or more rotary decks having mechanically or hydraulically driven blades; and one or more lift arms (or analogous structures) pivotally connected to the traction vehicle suitable for supporting the deck(s). Lift arms are so termed because they lift the decks from their normal operating positions to their transport positions, as further discussed below. The present invention involves methods and apparatus for supporting cutting units, and more particularly, lift arms and related structures and systems. More particularly, the present invention is directed toward methods and apparatus for supporting cutting units in their lowered operative positions and in their raised "transport" positions, and for raising and lowering cutting unit between the two extremes.
The preferred characteristics or features of a cutting unit support system vary depending on whether the cutting unit is in its cutting position or in its transport position. In the cutting position, the cutting units are preferably "floated" relative to the traction vehicle. That is, the cutting units are preferably independently and separately supported by the traction vehicle so they can follow the contours or undulations of the ground irrespective of the gross motion of the traction vehicle. If cutting units are not supported in a floating manner, they tend to scalp the higher regions and miss the lower regions. While non-floating cutting units might be acceptable for residential use, certainly golf course and estate maintenance require that the cutting units individually follow the subtle variations of the ground to maintain a consistently good cut across the entire swath, regardless of the immediate topography encountered by each individual cutting unit.
In addition to floating, applicants perceive that cutting units should be attached to the traction vehicle such that they are not permanently damaged if they should collide with an immovable object, such as a tree, during operation. When the cutting units of prior art mowers encountered immovable objects during mowing operations, they or their support structures, or both, were oftentimes severely damaged. Applicants perceive that cutting unit should be mounted such that they can temporarily "breakaway" from their normal operating positions in the event of such an impact. Further, the cutting units should be easily reset into their normal positions following the collision.
Another preferred feature of a cutting unit support system is the ability to support a wing or outboard cutting unit such that its outermost tip is readily observable by the operator, permitting the wing decks to be used for precise trimming. While this feature may seem obvious at first glance, prior art machines have generally not provided it, presumably because if the wing decks extend laterally outward from the operator's set the operator's side-to-side vision is greatly reduced when the decks are in their raised transport positions. Reference is made to FIGS. 1B and 2B, which show prior art units and the extent to which the operator's field of vision is reduced in transport mode. FIG. 1B illustrates a mower of the type sold by Jacobsen under the HR-15 designation; and FIG. 2B illustrates a mower of the type sold by Howard Price under the Hydro-Power 180 designation. The operator's side-to-side vision is almost completely blocked with the HR-15; whereas some side-to-side and some rear vision are blocked by the wing decks of the Hydro-Power 180.
The connection between the cutting units and the traction vehicle must also permit, if not assist, lifting of the cutting units from their lowered cutting positions to their raised transport positions. The operator might want to temporarily raise one or more of the cutting units to mow a narrower swath or to pass through a gate or between trees. Also, it is occasionally necessary to drive mowing machines over conventional road surfaces, at which time it is important to raise the cutting units to a transport position since they are not entirely suitable for repeatedly running up and down over curbs, nor for travel over paved streets at anything approaching the speed of ordinary city traffic. In view of this, most riding mowers, such as the one described in U.S. Pat. No. 2,299,859, include mechanisms which can raise the cutting units upward and toward the traction vehicle.
Once the cutting unit is raised into its transport position a preferred support system provides several important features. For example, when a cutting unit is in its raised or transport position, it must be held there very securely. Otherwise, it may tend to swing or rock and thereby cause personal injury or damage to the mower. For mowers having hydraulically-operated lift arms, additional mechanical latches or locks have traditionally been used to hold the lift arms in their raised or transport positions. This is due to the fact that some hydraulic cylinders are incapable of holding lift arms and cutting units in their raised positions because of hydraulic fluid leakage over a period of time.
As noted above, when the cutting units are in their raised transport positions the operator should preferably still have a 360.degree. field of vision. Reference is again made to the prior art designs of FIGS. 1B and 2B.
Also, when the cutting units are in their raised positions the center of gravity of the entire machine should not be too high, for otherwise the machine will not be able to safely negotiate sidehills and the like. Particularly for a front drive, rear steer mower, some of the weight of the wing decks should be borne by the rear wheels when the machine is in its transport mode, for otherwise the back end of the mower can literally lift off the ground when the mower is suddenly stopped for any reason. Prior art machines were not well balanced in the transport mode. For example, little if any of the weight of the HR-15 wing decks (see FIG. 1B) is borne by the rear steerable wheels.
Finally, Applicants perceive that when the lateral or wing cutting units are raised the overall width of the mower should preferably be less than the width of the front deck to permit close trimming with the front deck only. FIGS. 1A and 2A show top views of the HR-15 and Hydro-Power 180 mowers with the deck in transport mode. Of particular note is the fact that the raised wing decks extend beyond the outer edges of the front decks, thus hindering trimming.
The present invention addresses the problems associated with prior art cutting unit support systems. In particular, the cutting unit support system of the present invention accommodates deck floating and breakaway in the cutting position; and securely holds the cutting units, maintains a relatively low center of gravity, and maximizes the operator's field of vision in the transport position.